# Lesson 8

Suma de fracciones

### Lesson Purpose

### Lesson Narrative

Previously, students decomposed non-unit fractions into smaller unit and non-unit fractions. Here they continue to think about decomposing fractions, but they now use number line diagrams to support their reasoning.

A number line can illustrate the number of unit fractions that make a whole number. This in turn allows students to see that a fraction greater than 1 can be decomposed into a whole number and a fraction less than 1, preparing them to work with **mixed numbers**. For instance, on a number line partitioned into fifths, the fraction \(\frac{7}{5}\) is 7 fifths away from 0 and 2 fifths away from 1, so we can express \(\frac{7}{5}\) as 1 and \(\frac{2}{5}\). One way to illustrate that sum is by drawing “jumps” on the number line.

Note that in grade 3, students came across mixed numbers in the context of measurement. For instance, they use inch rulers to measure lengths greater than 1 inch to the nearest halves and fourths, express them using numbers such as \(2\frac{1}{4}\) and \(5\frac{1}{2}\). They did not, however, reason about mixed numbers as sums of smaller fractions or sums of a fraction and a whole number.

- Action and Expression

- MLR8

### Learning Goals

Teacher Facing

- Decompose fractions greater than 1 into a sum of a whole number and a fraction less than 1.
- Reason about addition of fractions with the same denominator using a number line.

### Student Facing

- Exploremos sumas de fracciones en una recta numérica.

### Required Materials

Materials to Copy

- Make Two Jumps

### Required Preparation

Activity 3:

- Create a set of cards from the blackline master for each group of 2.

### CCSS Standards

### Lesson Timeline

Warm-up | 10 min |

Activity 1 | 20 min |

Activity 2 | 15 min |

Activity 3 | 20 min |

Lesson Synthesis | 10 min |

Cool-down | 5 min |

### Teacher Reflection Questions

### Suggested Centers

- Rolling for Fractions (3–5), Stage 2: Multiply a Fraction by a Whole Number (Addressing)
- Estimate and Measure (1–4), Stage 3: Quarter Inches (Supporting)
- Target Measurements (2–5), Stage 2: Quarter Inches (Supporting)

### Print Formatted Materials

Teachers with a valid work email address can click here to register or sign in for free access to Cool Down, Teacher Guide, and PowerPoint materials.

Student Task Statements | docx | |

Lesson Cover Page | docx | |

Cool Down | Log In | |

Teacher Guide | Log In | |

Teacher Presentation Materials | docx | |

Blackline Masters | zip |